Changes

==Chemical Properties==

==Chemical Properties==

At normal pressures hydrogen melts at 14.01 [[Kelvin]] (K) and boils at 20.28 K, essentially meaning that it only exists on Earth as a gas. The near-vacuum of interstellar space means that hydrogen is also a gas under these circumstances. Astronomers and chemists hypothesise that hydrogen exists as a plasma inside stars and possibly in a metallic form in the cores of gas giant [[planets]] such as [[Jupiter]]. The most common form of hydrogen is molecular hydrogen, consisting of two atoms bonded by a single covalent bond. The chemical symbol for molecular hydrogen is H₂.

At normal pressures hydrogen melts at 14.01 [[Kelvin]] (K) and boils at 20.28 K, essentially meaning that it only exists on Earth as a gas. The near-vacuum of interstellar space means that hydrogen is also a gas under these circumstances. Astronomers and chemists hypothesize that hydrogen exists as a plasma inside stars and possibly in a metallic form in the cores of gas giant [[planets]] such as [[Jupiter]]. The most common form of hydrogen is molecular hydrogen, consisting of two atoms bonded by a single covalent bond. The chemical symbol for molecular hydrogen is H₂.

Due to having the lowest possible atomic number hydrogen is the lightest element. As a result of this it was used in many early airships and balloons, but due to the dangers involved it has been replaced by [[helium]] in these applications.

Due to having the lowest possible atomic number hydrogen is the lightest element. As a result of this it was used in many early airships and balloons, but due to the dangers involved with its flammability, it has been replaced by [[helium]] in these applications.

==Isotopes==

==Isotopes==